rtla/trace: Add trace event trigger helpers

Add a set of helper functions to allow rtla tools to trigger event
actions in the trace instance.

Link: https://lkml.kernel.org/r/e0d31abe879a78a5600b64f904d0dfa8f76e4fbb.1646247211.git.bristot@kernel.org

Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Clark Williams <williams@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Author: Daniel Bristot de Oliveira

tools/tracing/rtla/src/trace.c

@@ -204,6 +204,8 @@ static void trace_events_free(struct trace_events *events)
 
 		tevent = tevent->next;
 
+		if (free_event->trigger)
+			free(free_event->trigger);
 		free(free_event->system);
 		free(free_event);
 	}
@@ -235,6 +237,48 @@ struct trace_events *trace_event_alloc(const char *event_string)
 	return tevent;
 }
 
+/*
+ * trace_event_add_trigger - record an event trigger action
+ */
+int trace_event_add_trigger(struct trace_events *event, char *trigger)
+{
+	if (event->trigger)
+		free(event->trigger);
+
+	event->trigger = strdup(trigger);
+	if (!event->trigger)
+		return 1;
+
+	return 0;
+}
+
+/*
+ * trace_event_disable_trigger - disable an event trigger
+ */
+static void trace_event_disable_trigger(struct trace_instance *instance,
+					struct trace_events *tevent)
+{
+	char trigger[1024];
+	int retval;
+
+	if (!tevent->trigger)
+		return;
+
+	if (!tevent->trigger_enabled)
+		return;
+
+	debug_msg("Disabling %s:%s trigger %s\n", tevent->system,
+		  tevent->event ? : "*", tevent->trigger);
+
+	snprintf(trigger, 1024, "!%s\n", tevent->trigger);
+
+	retval = tracefs_event_file_write(instance->inst, tevent->system,
+					  tevent->event, "trigger", trigger);
+	if (retval < 0)
+		err_msg("Error disabling %s:%s trigger %s\n", tevent->system,
+			tevent->event ? : "*", tevent->trigger);
+}
+
 /*
  * trace_events_disable - disable all trace events
  */
@@ -248,14 +292,52 @@ void trace_events_disable(struct trace_instance *instance,
 
 	while (tevent) {
 		debug_msg("Disabling event %s:%s\n", tevent->system, tevent->event ? : "*");
-		if (tevent->enabled)
+		if (tevent->enabled) {
+			trace_event_disable_trigger(instance, tevent);
 			tracefs_event_disable(instance->inst, tevent->system, tevent->event);
+		}
 
 		tevent->enabled = 0;
 		tevent = tevent->next;
 	}
 }
 
+/*
+ * trace_event_enable_trigger - enable an event trigger associated with an event
+ */
+static int trace_event_enable_trigger(struct trace_instance *instance,
+				      struct trace_events *tevent)
+{
+	char trigger[1024];
+	int retval;
+
+	if (!tevent->trigger)
+		return 0;
+
+	if (!tevent->event) {
+		err_msg("Trigger %s applies only for single events, not for all %s:* events\n",
+			tevent->trigger, tevent->system);
+		return 1;
+	}
+
+	snprintf(trigger, 1024, "%s\n", tevent->trigger);
+
+	debug_msg("Enabling %s:%s trigger %s\n", tevent->system,
+		  tevent->event ? : "*", tevent->trigger);
+
+	retval = tracefs_event_file_write(instance->inst, tevent->system,
+					  tevent->event, "trigger", trigger);
+	if (retval < 0) {
+		err_msg("Error enabling %s:%s trigger %s\n", tevent->system,
+			tevent->event ? : "*", tevent->trigger);
+		return 1;
+	}
+
+	tevent->trigger_enabled = 1;
+
+	return 0;
+}
+
 /*
  * trace_events_enable - enable all events
  */
@@ -275,6 +357,10 @@ int trace_events_enable(struct trace_instance *instance,
 		}
 
 
+		retval = trace_event_enable_trigger(instance, tevent);
+		if (retval)
+			return 1;
+
 		tevent->enabled = 1;
 		tevent = tevent->next;
 	}

tools/tracing/rtla/src/trace.h

@@ -6,7 +6,9 @@ struct trace_events {
 	struct trace_events *next;
 	char *system;
 	char *event;
+	char *trigger;
 	char enabled;
+	char trigger_enabled;
 };
 
 struct trace_instance {
@@ -40,3 +42,5 @@ void trace_events_destroy(struct trace_instance *instance,
 			  struct trace_events *events);
 int trace_events_enable(struct trace_instance *instance,
 			  struct trace_events *events);
+
+int trace_event_add_trigger(struct trace_events *event, char *trigger);